The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a fiber optic sensing system and method for measuring properties, such as heat transfer characteristics, of substances and environments in wells and other locations.
It is frequently desirable to be able to detect or measure various properties of substances in a well. For example, it may be desirable to determine a rate of flow of fluid from a producing zone, determine the composition of a fluid mixture in the well, evaluate the quality of a cementing operation, locate a fluid interface (i.e., liquid/liquid or gas/liquid) in the well or in a formation intersected by the well, etc.
Typically, certain measurements are made by conveying a logging tool into the well and using sensors, such as flowmeters and thermocouples, to detect properties of fluid in the well. Unfortunately, the logging tool obstructs a passage for flow of fluid in the well, thereby interfering with production. It is also somewhat time-consuming and costly to make such logging trips into the well. This is particularly so if it is desired to periodically perform the measurements to track changes in the well over time, such as to evaluate the migration of an oil/water interface in a formation drained by the well.
Some fiber optic measurement systems have been developed for permanent installation in a well. However, these are very expensive, and their principles of operation make the measurements obtained using these systems possibly unreliable at certain flow rates, flow regimes and/or hydrocarbon combinations, etc.
Therefore, it may be seen that it would be beneficial to provide improved systems and methods for sensing properties of substances in a well. These systems and methods would preferably, but not necessarily, eliminate any obstruction to fluid flow through the well, be configured for permanent installation in the well, be convenient in use and provide reliable results.
Furthermore, it would be desirable for such systems and methods to be versatile in application to, for example, pipelines, chemical processes, on the surface, remotely controlled and/or monitored, etc. Other examples include production infrastructure immediately downstream of a well, e.g., sea bed flowlines and manifolds, subsea or surface wellheads, risers and production platform pipes. Sensing systems installed at these locations may be used along with other sensors for monitoring of production parameters, as well as formation and deposition of waxes, asphaltines and hydrates.